Method and apparatus for producing an assembly by friction welding

ABSTRACT

Cluster gear assemblies are produced by a method and apparatus which join a plurality of premachined gears by a common joining member. The plurality of gears are held in relative nonrotative relationship by special holding means which further establish precise angular and axial alignment between the gears and axial alignment between the joining member and the gears. Joining of the various members to produce the assembly is accomplished by friction welding.

United States Patent 11 1 Satzler et aL METHOD AND APPARATUS FOR PRODUCING AN ASSEMBLY BY FRICTION WELDING [75] Inventors: Ronald L. Satzler. Metamora;

Marion R. Calton, East Peoria, both [73] Assignee: Caterpillar Tractor Co., Peoria, 111. [22] Filed: July 15, 1974 [21 Appl. No.: 488,704

Related U.S. Application Data [62] Division of Ser. No. 344,979, March 26, 1973, Pat. No. 3,831,459, which is a division of Ser No, 148,780, June 1, 1971, Pat. No. 3,750,263.

[52] U.S. Cl. 228/2; 29/4703; 156/735 [51] Int. Cl 823k 27/00 [58] Field of Search 228/2; 29/4703, 159.2; 156/735 [56] References Cited UNITED STATES PATENTS 3,504,425 4/1970 Sutovsky et a1 228/2 X 1 1 Aug. 5, I975 3.571,906 3/1971 Barth et a1. .1 228/2 X 3,618,196 11/1971 Sluetz 1. 3,763,549 10/1973 Bonneville et all 29/4703 Primary E.\'uminerAl Lawrence Smith Axsismm E.mm[nerMargaret M. Joyce Attorney, Agent, or FirmPhillips, Moore, Weissenberger Lempio & Strabala [57) ABSTRACT Cluster gear assemblies are produced by a method and apparatus which join a plurality of premachined gears by a common joining member, The plurality of gears are held in relative nonrotative relationship by special holding means which further establish precise angular and axial alignment between the gears and axial alignment between the joining member and the gears. Joining of the various members to produce the assembly is accomplished by friction welding.

1 Claim, 7 Drawing Figures PATENTED AUB 51975 SHEET PATENTEU AUG 5 I975 SHEET 2 PATENTED AUG 5 I 75 SHEET PATENTEU AUB 5 I975 SHEET METHOD AND APPARATUS FOR PRODUCING AN ASSEMBLY BY FRICTION WELDING This is a division, of Ser. No. 344,979, filed Mar. 26, 1973 now US. Pat. No. 3,831 ,459; which is a divisional of Ser. No. 148,780, filed on June I, 1971, now US. Pat. No. 3,750,263.

BACKGROUND OF THE INVENTION Friction welding is a well-known method of joining individual pieces into an assembly. However, this method has been limited in the past to joining pieces which required no specific angular alignment between the individual pieces of the completed assembly, since it is extremely difficult to stop a rotating piece in an exact position. Because of this problem, most assemblies which require angular alignment between individual pieces are not joined by friction welding. Many such assemblies are produced by machining the entire assembly from one original piece. One example of this type of assembly is a cluster gear.

Cluster gear assemblies form a necessary portion of most transmission units, although they are expensive to produce and add bulk and weight to a unit. Present technology for manufacturing cluster gears utilizes a forging process whereby a gear blank is forged from a single slug of metal. The gear teeth are not formed on the forging but are machined in subsequent machining operations. Much of the expense of producing cluster gear assemblies relates to the time-consuming method of machining teeth on adjacent gears specifically where those gears necessarily have different outside diameters. The teeth on the largest gear in the cluster can be machined by a fast and economical hobbing operation. However, the teeth on the smaller gears in the cluster usually must be machined by slow and expensive shaping and shaving operations. The extra bulk and weight are the result of providing clearance between the adjacent gears to accommodate various types of cutting tools for machining the gear teeth.

SUMMARY AND OBJECTS OF THIS INVENTION Briefly described, this invention relates to a method of producing an improved cluster gear assembly. To produce this assembly, special holding means are provided to hold a plurality of individual premachined gear members in an exact angular and axial position while a joining member is simultaneously friction welded to each of the gear members. Friction welding of the conventional or the inertia type may be used. It is, therefore, an object of this invention to overcome the above briefly described problems by providing methods and apparatus for joining a plurality ofindividual parts into an assembly.

It is also an object of this invention to join a plurality of members which require angular alignment by a method in which no relative motion between the plurality of members is permitted.

It is another object of the invention to join a plurality of individual finished, or semifinished, gears into a cluster unit.

It is a further object of this invention to construct an improved cluster gear assembly which is lighter in weight and less costly to produce than known cluster gear assemblies.

A still further object of this invention is an apparatus which will hold members to be joined in an exact angular and axial position.

It is also an object of the invention to form a cluster gear assembly by joining the parts of the assembly by the friction or inertia welding processes.

These and other objects of the invention will become apparent to those skilled in the art upon examination of the following description of the preferred embodiments thereof as depicted in the drawings, which are intended to illustrate but not restrict the scope of this invention. It is recognized that other embodiments of the invention may be used and structural changes may be made by those skilled in the art without departing from the scope of the present invention and the pur view of the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a side elevation illustrating one embodiment of a friction welding machine which may be used to practice the method of the present invention;

FIG. 2 is a fragmentary side view, partially in section, illustrating workpiece holding fixture parts and appara' tus constructed in accordance with one embodiment of the invention;

FIG. 3 is a top plan view of the joining member of FIG. 2;

FIG. 4 is a cross-sectional view of a gear assembly joined in accordance with another embodiment of the invention;

FIG. 5 is a cross-sectional view of another gear assembly joined in accordance with one embodiment of the invention;

FIG. 6 is a cross-sectional view of a gear assembly joined in accordance with still another embodiment of the invention;

FIG. 7 is a cross'sectional view of another gear assembly joined in accordance with one embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT A friction welding machine, constructed in accordance with one exemplary embodiment of the present invention is indicated generally by the reference number 10 in FIG. I of the drawings. As illustrated, the friction welding machine I0 comprises a frame or housing structure 12 for housing the various components of the machine. Within the housing of the machine, an electric motor 14 powers a hydrostatic transmission generally denoted by reference numberal I6. The hydro static transmission 16 includes a hydraulic pump 18 and a hydraulic motor 20, operably connected by a manifold or conduits 22. The hydraulic motor 20 is connected to a spindle assembly 24 which is mounted for rotation within the machine frame I2.

A rotary holding fixture 26 is mounted on the spindle assembly 24 and rotates with the spindle. An exemplary workpiece WP-l is securely held within the rotary fixture 26.

A second workpiece WP-Z is securely held in a nonrotary fixture 28 attached to a tailstock fixture 30 which is mounted on the frame 12.

The tailstock fixture 30 is mounted for axial movement on the machine frame by a load cylinder assembly 32.

A pressure control circuit, not shown, regulates the pressure in the load cylinder and thus determines the force with which the parts WP-] and WP-Z are engaged.

The hydrostatic transmission assembly 16 can be used to vary the drive ratio between the motor and the spindle assembly 24 and can also be used to effectively disconnect the spindle assembly from the motor. Various other means could also be used to disconnect the spindle from the motor, including many types of available clutches.

lt is to be understood that flywheel weights, although not shown, could be mounted to the rotary holding fixture 26 so that the welding machine can be operated as an inertia welding machine, as described in U.S. Pat. No. 3,273,233, and as further described in detail below. It is also to be understood that the workpieces WP-] and WP2 shown in FIG. 1 are exemplary only and do not necessarily represent the exact configura tion of the workpieces to be welded within the scope of this invention. A more detailed description of several workpiece configurations will be given with reference to FIGS. 2, 3, 4 and 5 in the drawings.

With continued reference to FIG. I, a welding operation for joining two workpieces WP-l and WP-2 together is performed by operating the machine in the following general manner.

One of the workpieces, WP-l, is secured within the rotatable holding fixture 26 on the spindle assembly 24. The other workpiece, WP-2, is secured within the nonrotatable holding fixture 28 which is further fastened to the tailstock assembly 30. The load cylinder 32 is then activated to move the tailstock assembly 30 toward the spindle 24 until the workpieces WP-l and WP-Z are in close proximity, but are not in contact with each other. The motor 14 is then activated and the spindle assembly 24 and rotatable holding fixture 26 are accelerated by means of the hydrostatic transmission assembly 16 which is coupled to the electric motor 14.

When the predetermined and preset velocity is reached by the rotating fixture 26, appropriate controls shut down or disconnect the electric motor 14 from the spindle assembly 24, and at the same time activate the load cylinder 32 to move the tailstock fixture 30 forward. workpiece WP-2 is thereby brought into contact under pressure with the rapidly rotating workpiece WP], and heat is generated by friction at the contacting surfaces of the two workpieces. This heating continues until the workpieces reach the weld temperature at which time the upsetting pressure, applied by the load cylinder 32 at a constant or varying pressure, causes flashing or upsetting to occur. During this period of heating and flashing, the rotational velocity of the spindle and holding fixture has continued to decrease.

At the time that rotation ceases, all of the stored en ergy in the rotating members has been converted to heat and forging at the weld interface and the weld is completed. The load cylinder 32 is then activated in a reverse direction and the complete welded assembly is removed from the holding fixtures of the machine. Although the inertia welding process has been described, it is recognized that other methods of friction welding may be used to practice the instant invention.

FIG. 2 illustrates one embodiment of the present invention consisting of a welded cluster gear assembly. The cluster gear assembly consists of a first premachined gear 40, a second premachined gear 42, and a rotatable joining member 44 which serves to join all members together into an assembly.

The two gears 40 and 42 are held together in a special nonrotatable fixture 28.

The rotatable joining member 44 is held in a special rotatable holding fixture 26.

Fixture 28 is in turn securely fastened to the tailstock portion 30 of a welding machinev Fixture 26 is securely fastened to the rotatable spindle of a friction welding machine (refer to FIG. 1).

At this point, it should be stated that it would be possible, and in some instances desirable, to rotate the gears 40 and 42, by rotating fixture 28 and hold the joining member 44 against rotation. The only requirement is that relative rotary motion be imparted between the plurality of members (gears, in this case) and the joining member.

Fixture 28 contains two counterbores 46 and 48 with internal teeth 50 and S2 machined in the respective counterbores. Internal teeth 50 are machined to match and mesh with the external teeth 54 of gear 40, and internal teeth 52 are machined to match and mesh with external teeth 56 on gear 42. In this way, both gears 40 and 42 are prevented from rotating and any angular alignment between the two gears can be obtained by machining the internal teeth in the fixtur: 28 to produce the desired alignment. Axial alignruc it between gears 40 and 42 is also attained be proper machining of the counterbores and internal teeth of fixture 28.

The joining member 44 is essentially a tubular member with an internal bore 58 which closely matches the bore 60 of gear 40.

The member 44 further contains a plurality of flats 62, which together form a hexagonal shape and fit into a matching socket 64 of the holding fixture 26. In this way, the joining member 44 is securely held within the fixture 26 without the necessity of tightening any type of collet or jaws.

Although the joining member and fixture socket have been indicated as having a hexagonal configuration, any number of other type of configurations would work equally satisfactorily, such as square or octagonal. The end of the joining member opposite the hexagonal portion is of reduced diameter and contains a circular projection 66 which is slightly smaller in d ameter than the internal bore 68 of gear 42. In this way, the projection 66 extends through bore 68 and contacts surface 70 of gear 40 without making contact with the internal bore 68 of gear 42. The length of projection 66 is such that when it is inserted into bore 68 of gear 42, the end of the projection will contact surface 70 at or about the same time that contact is made between surface 72 of the joining member and surface 74 of gear 42.

At the beginning of a welding operation to join the two gears and the joining member into a cluster gear assembly, a small gap exists between the projection 66 and surface 70 as well as between surfaces 72 and 74. ln this way, the joining member can be accelerated to the welding speed without friction developing due to contacting surfaces. However, once the welding velocity has been reached, the load cylinder is activated to bring the rotating joining member into contact with both nonrotating gears 40 and 42. A weld is thereby accomplished between projection 66 of the joining member and the surface 70 of gear 40, and between surface 72 of the joining member and surface 74 of the gear 42. Although no actual weld exists between the two gears 40 and 42, they are rigidly joined by the member 44 since a separate area of the joining member 44 is welded to each of the gears 40 and 42.

During the application of the welding thrust force, gear 40 is supported by a projection 76 within fixture 28, and gear 42 is supported against the thrust by the gear 40.

A chamber 78 on gear 42 forms a flash trap to accommodate the external flash produced between the joining member 44 and gear 40.

Likewise, a machined groove 80 in the joining member 44 accommodates the internal flash produced between member 44 and gear 42.

The external flash produced when surface 72 of member 44 is welded to surface 74 of gear 42, can remain on the gear assembly since it is in an area which will cause no problems. However, the internal flash produced between member 44 and gear 40, which will flow into the bores 58 and 60, will need to be removed since these bores must accommodate a shaft. This flash removal will present no problem since these bores must be finished machined prior to final assembly of the cluster gear unit into a transmission.

FIG. 3 illustrates a top plan view of the joining member shown in FIG. 2. As previously mentioned, the joining member 44 is provided with a hexagonal shape by flats 62 for easy insertion into and removal from the rotatable holding fixture 26. The hexagonal portion 62 in cooperation with socket 64 provides a positive driving connection between the joining member 44 and fixture 26 during acceleration and to absorb the torque devel oped during the friction welding operation.

Alternatively, joining member 44 could be held in any suitable manual or power-operated chucking device to eliminate the necessity of producing a noncircular shape at the one end of the joining member.

Since the teeth of the two gears 40 and 42 are machined prior to welding, no extra space is required between the gears to accommodate machining tools, as is required in the production of most cluster gear assemblies. This advantageously results in a high-strength, compact, lightweight assembly as compared with cluster gear assemblies produced by other methods. The total cost of producing a cluster gear assembly by the instant invention is also less than other known methods since less costly machining operations can be used to machine the gears before welding.

Referring to FIG. 4 of the drawings, a slightly different embodiment of the invention is illustrated. In this embodiment, a joining member 86 is used to join three separate gear members 88, 90 and 92 into a cluster assembly. In this assembly three surfaces 94, 96, and 98 of the joining member are welded to respective surfaces 100, I02, and 104 of gears 88, 90, and 92.

Small pockets 106 in the joining member and grooves 108 in gears 88, 90, and 92 cooperate to form flash traps for the flash produced during the welding.

Any required angular alignment between gears 88, 90, and 92, can, of course, be provided by a special holding fixture, similar to fixture 28 in FIG. 2. Axial alignment between all members of the assembly is provided by the two fixtures holding the rotary and nonrotary members. A central bore 112 in the joining member 86 can provide for the mounting of the completed assembly on a shaft.

FIG. 5 illustrates an alternate assembly joined in accordance with the embodiment shown and described in reference to FIG. 2. However, the completed assembly of FIG. 5 comprises a herringbone gear rather than a cluster assembly. The herringbone gear assembly 116 consists of two helical gears 118 and I20 and a joining member 122. In this assembly, surface 124 of joining member 122 is welded to surface 126 of gear 118 and surface I28 of member I22 is welded to surface 130 of gear 120.

The herringbone gear is a very special type of gear and is extremely expensive to produce using present manufacturing technology. However, by joining two premachined helical gears, one left hand and one right hand, using the methods and apparatus of the present invention, an inexpensive herringbone gear is produced.

FIGS. 6 and 7 illustrate alternate designs, respectively, ofa cluster gear assembly I36 and a herringbone gear assembly I38 produced in accordance with the present invention. Assembly 136 comprises a joining member I40 and three gear-like members, I42, I44 and 146. An outer conical-shaped surface I48 of the joining member 140 contains a plurality of longitudinally spaced parallel projections I50, 152 and I54, which extend radially outward.

Member 142 contains two radially extending parallel end surfaces 156 and I58, a central tapered bore I60, and a projection 162 extending radially inward from the central bore. Member 144 also contains two radially extending parallel end surfaces I66 and I68, a central tapered bore 170, and a projection I72 extending radially inward from the central bore. Likewise, mem ber 146 contains two radially extending parallel end surfaces 176 and 178, a central tapered bore 180 and a projection I82 extending radially inward from the central bore.

The three projections 162, I72 and I82 contain respectively tapered surfaces 184, I86 and 188 which match tapered surfaces 190, I92 and I94, respectively, of joining member projections 150, I52, and I54. The joining members 140 and the three gear members 142, 144, and I46 are welded into assembly 136 by the previously described method wherein the three gear members are held in a non-rotating fixture (not shown) and the joining member is held in the rotatable fixture of a friction welding machine (not shown).

A special non-rotating holding fixture will secure the three gear members I42, I44 and I46 in whatever angular alignment is desired. Once secured in the fixture, surface 158 of member 142 is in contact with surface 166 of member 144 and surface I68 of member I44 is in contact with surface 176 of member 146. Actual welding between the joining member and the other members takes place at the contact areas between tapered surfaces 184, I86 and I88 of the gear members and matching tapered surfaces I90, I92 and 194 ofthe joining member.

In the completed assembly, two sealed pockets I96 and I98 are formed between joining member and the other members. Much of the flash produced during welding will be contained within these pockets and will, of course, need not be removed. Likewise, the flash at the other weld areas, which is not sealed within pockets I96 and 198, is in a recessed area and will, most likely, not require removal.

FIG. 7 illustrates the design of FIG. 6 adapted to a herringbone gear assembly 138. In this embodiment, a left hand helical gear member 202 and a right hand helical gear member 204 are held in a non-rotatable fixture (not shown) while a joining member 206, held in the rotatable portion of a friction welding machine (not shown) is welded to the two gear members. As in the embodiment of FIG. 6, welding takes place between matching tapered surfaces on projections 208 and 210 of members 202 and 204 and projections 2l2 and 214 of joining member 206.

While the subject invention has been illustrated and described with particular reference to cluster gear assemblies, it is to be understood that other types of assemblies could be joined by using the disclosed method and apparatus. Therefore, we do not wish to be limited to the precise details set forth, but desire to avail ourselves of such changes and alterations which fall within the purview of the following claims.

What is claimed is:

l. A friction welding machine for welding cluster gears and comprising, a first fixture having a plurality of axially spaced gear retaining rings and an axial thrust back-up surface each of said retaining rings having inwardly projecting elements adapted to engage the outwardly projecting teeth of a cluster gear, a second fixture having a recessed, non-circular opening shaped to provide both rotational driving torque and axial thrust to a complementary shaped end of a gear connecting member, and means for applying relative axial and rotary movements between said fixtures to accomodate a friction welding engagement between the gears and the connecting element, whereby the gears can be held in the first fixture in predetermined angular alignment and can be welded together by the gear connecting element without any clamping action in the fixtures. 

1. A friction welding machine for welding cluster gears and comprising, a first fixture having a plurality of axially spaced gear retaining rings and an axial thrust back-up surface, each of said retaining rings having inwardly projecting elements adapted to engage the outwardly projecting teeth of a cluster gear, a second fixture having a recessed, non-circular opening shaped to provide both rotational driving torque and axial thrust to a complementary shaped end of a gear connecting member, and means for applying relative axial and rotary movements between said fixtures to accomodate a friction welding engagement between the gears and the connecting element, whereby the gears can be held in the first fixture in predetermined angular alignment and can be welded together by the gear connecting element without any clamping action in the fixtures. 